Upper Body Exoskeleton for Stroke Rehabilitation Research
Back in 2014 while I was working for Meka Robotics we were approached by university researchers that had funding to develop an upper body exoskeleton for stroke rehabilitation. This new system would provide many new ways to perform rehab from mirroring one arm to the other to impedance controlled movement patterns and strength/ROM measuring. They had detailed out a kinematic model showing what they wanted to achieve. It was my job to take that “stick figure” and detail out and build a system based on their geometry. Here’s some pics and details on how that went.
Bringing Up Actuation
This system leveraged Meka’s series elastic actuators. It contained 14 actuators capable of smooth position and torque control. When building up a system like this I like to build up what’s called the ‘roadkill’ setup. each actuator is built and wired to its respective motor controller so that each actuator can be brought up and validated while other hardware like the main structure is being manufactured.
Staging the components
Another tool that is critical when building a project as complex as this is keeping your parts organized and coming up with a clear workflow. After releasing the parts to manufacture you can get a clear idea of when each component will arrive. Based on that, you can detail out an assembly process that will allow quick yet meticulous assembly. Due to long lead times I ordered the actuation and bearing components first. These items can take upwards of 8 weeks to arrive so sometimes they have to be purchased before the final design is even finished. After that, the large machined components had to be purchased and staged. In the middle, I like to get parts in that I’m unsure on. One such part is the threaded rods that act as the clavicle on this robot. I really wanted to test this before I went too far down the rabbit hole (pictured here).
More Organization
To reiterate how important organizing is when building a system like this, I’ve included another shot showing the layout of all of the components. They’re arranged based on sub-assembly to help me easily see what’s here, what needs to be finished. One of the joys of designing and building is that the design is still in your head so keeping parts sorted is quite easy.
Assembly
There are lots of steps when it comes to assembly. So many best practices to keep in mind. Thermal management, fastener retention, cable routing, lubrication, et. On a mass produced machine these have generally had teams of people looking over them. For a one of kind build, you have to really think these through beforehand. The “just fix it in post” doesn’t really work well in hardware.
Shoulder Up and Moving.
Assembled one shoulder and did some early testing to see it move. There are 5 degrees of freedom in the shoulder. Shrug, shoulder forward and back, then three actuators to make the ball joint of the shoulder. Lots going on in there.